Buggy code:
public class FieldReference extends Reference implements InvocationSite { public Expression receiver ; public char [ ] token ; public FieldBinding binding ; protected FieldBinding codegenBinding ; public MethodBinding [ ] syntheticAccessors ; public static final int READ = 0 ; public static final int WRITE = 1 ; public long nameSourcePosition ; public TypeBinding receiverType ; public TypeBinding genericCast ; public FieldReference ( char [ ] source , long pos ) { } public FlowInfo analyseAssignment ( BlockScope currentScope , FlowContext flowContext , FlowInfo flowInfo , Assignment assignment , boolean isCompound ) { } public FlowInfo analyseCode ( BlockScope currentScope , FlowContext flowContext , FlowInfo flowInfo ) { } public FlowInfo analyseCode ( BlockScope currentScope , FlowContext flowContext , FlowInfo flowInfo , boolean valueRequired ) { } public void computeConversion ( Scope scope , TypeBinding runtimeTimeType , TypeBinding compileTimeType ) { } public FieldBinding fieldBinding ( ) { } public void generateAssignment ( BlockScope currentScope , CodeStream codeStream , Assignment assignment , boolean valueRequired ) { } public void generateCode ( BlockScope currentScope , CodeStream codeStream , boolean valueRequired ) { } public void generateCompoundAssignment ( BlockScope currentScope , CodeStream codeStream , Expression expression , int operator , int assignmentImplicitConversion , boolean valueRequired ) { boolean isStatic ; receiver . generateCode ( currentScope , codeStream , ( ! ( isStatic = this . codegenBinding . isStatic ( ) ) ) ) ; if ( isStatic ) { if ( ( ( syntheticAccessors ) == null ) || ( ( syntheticAccessors [ FieldReference . READ ] ) == null ) ) { codeStream . getstatic ( this . codegenBinding ) ; } else { codeStream . invokestatic ( syntheticAccessors [ FieldReference . READ ] ) ; } } else { codeStream . dup ( ) ; if ( ( ( syntheticAccessors ) == null ) || ( ( syntheticAccessors [ FieldReference . READ ] ) == null ) ) { codeStream . getfield ( this . codegenBinding ) ; } else { codeStream . invokestatic ( syntheticAccessors [ FieldReference . READ ] ) ; } } int operationTypeID ; <START_BUG> if ( ( operationTypeID = ( implicitConversion ) > > 4 ) == ( T_String ) ) { <END_BUG> codeStream . generateStringConcatenationAppend ( currentScope , null , expression ) ; } else { codeStream . generateImplicitConversion ( implicitConversion ) ; if ( expression == ( IntLiteral . One ) ) { codeStream . generateConstant ( expression . constant , implicitConversion ) ; } else { expression . generateCode ( currentScope , codeStream , true ) ; } codeStream . sendOperator ( operator , operationTypeID ) ; codeStream . generateImplicitConversion ( assignmentImplicitConversion ) ; } fieldStore ( codeStream , this . codegenBinding , ( ( syntheticAccessors ) == null ? null : syntheticAccessors [ FieldReference . WRITE ] ) , valueRequired ) ; } public void generatePostIncrement ( BlockScope currentScope , CodeStream codeStream , CompoundAssignment postIncrement , boolean valueRequired ) { } public TypeBinding [ ] genericTypeArguments ( ) { } public static final Constant getConstantFor ( FieldBinding binding , Reference reference , boolean isImplicit , Scope referenceScope ) { } public boolean isSuperAccess ( ) { } public boolean isTypeAccess ( ) { } public void manageSyntheticAccessIfNecessary ( BlockScope currentScope , FlowInfo flowInfo , boolean isReadAccess ) { } public StringBuffer printExpression ( int indent , StringBuffer output ) { } public TypeBinding resolveType ( BlockScope scope ) { } public void setActualReceiverType ( ReferenceBinding receiverType ) { } public void setDepth ( int depth ) { } public void setFieldIndex ( int index ) { } public void traverse ( ASTVisitor visitor , BlockScope scope ) { } }

Fix:
if ( ( operationTypeID = ( ( implicitConversion ) & ( TypeIds . IMPLICIT_CONVERSION_MASK ) ) > > 4 ) == ( T_String ) ) {